Sublingual immunotherapy (SLIT) involves taking extracts of allergens under the tongue, which triggers asthma and allergies and increases the tolerance to these triggers. It works in the same way that allergy shots reduce allergic sensitivity in many patients over time.
This type of treatment, known as immunotherapy, has been shown effective for allergic respiratory disease when given in injection form in studies. But the value of SLIT therapy for the treatment of asthma, especially in children, has been less clear.
Although a popular treatment for allergies and asthma in many European countries, sublingual therapy has not been approved for use in the U.S.
SLIT Reduces Asthma Symptoms
In the newly published analysis, researchers from Italy's University of Genoa combined the results of nine studies involving 441 children and teens with allergic asthma treated with either sublingual immunotherapy or placebo.
More side effects were seen in the SLIT-treated patients, but none involved anaphylaxis, which is a rare, potentially life-threatening complication of injection immunotherapy. The most common side effects noted in the SLIT-treated patients included oral symptoms, nose and eye symptoms, and gastrointestinal symptoms.
Researcher Martin Penagos, MD, and colleagues conclude that SLIT appears to be an effective and safe treatment in children, with the potential to reduce the severity of asthma symptoms over time.
"Due to the favorable safety profile and its potential in modifying the evolution of disease, SLIT is of relevant value in the treatment of asthma in association with standard drug therapy," they write in the March issue of the journal Chest.
Unanswered Questions About SLIT
Because SLIT does not require weekly or even twice-weekly visits to an allergist the way allergy shots do, it has the potential to greatly expand the pool of patients on immunotherapy for allergies and asthma, allergy and asthma specialist Linda S. Cox, MD, tells WebMD.
"Shots require a big commitment, and right now only about 5% of eligible patients in this country get them," she says. "Immunotherapy is the only treatment we have that modifies the course of the disease. Medications just treat symptoms."
In 2006, a task force made up of members of the nation's leading allergy and asthma groups weighed in on SLIT, concluding that there is clear evidence that oral immunotherapy is an effective treatment for allergic disease.
Cox led the task force, which also found that important questions about sublingual therapy remain unanswered.
Among the most important are the optimal dosage, treatment schedule, and length of treatment needed.
Dosages and treatment frequency and durations have varied widely in the studies reported to date, and few have compared different treatment protocols.
Though the risk of having a life-threatening allergic reaction to the treatment appears to be very low with oral immunotherapy, such reactions have been reported.
"We have to decide how to deal with that, since this is a treatment that is given at home," Cox says. "In Europe, it isn't recommended that patients have injectible epinephrine in the home (to treat anaphylaxis), but we may choose to be a little more conservative."